To identify viruses and compare their abundance levels in the venom glands of hymenopteran species, we conducted venom gland-specific transcriptome assemblies and analyses of 22 Aculeate bees and wasps and identified the RNA genomes of picornaviruses. Additionally, we investigated the expression patterns of viruses in the venom glands over time following capture. Honeybee-infecting viruses, including black queen cell virus (BQCV), deformed wing virus (DWV), and Israeli acute paralysis virus (IAPV), were highly expressed in the venom glands of Apis mellifera and social wasps. This finding suggests that the venoms of bees and wasps likely contain these viruses, which can be transmitted horizontally between species through their stinger usage. A. mellifera exhibited an increasing pattern of abundance levels for BQCV, DWV, IAPV, and Triatovirus, while the social wasp Vespa crabro showed increasing abundance levels of IAPV and Triatovirus over different capture periods. This suggests that the venom glands of honeybees and wasps may provide suitable conditions for active viral replication and may be an organ for virus accumulation and transmission. Some viral sequences clearly reflected the phylogeny of Aculeate species, implying host-specific virus evolution. On the other hand, other viruses exhibited unique evolutionary patterns of phylogeny, possibly caused by specific ecological interactions. Our study provides insights into the composition and evolutionary properties of viral genes in the venom glands of certain Aculeate bees and wasps, as well as the potential horizontal transmission of these viruses among bee and wasp species.

Pyrethroid resistance in cockroach populations has been a public health challenge since the 1950s. The pyrethroid resistance in the German cockroach, Blattella germanica, is primarily attributed to knockdown resistance (kdr) mutations (E434K, C764R, and L993F) in the voltage-sensitive sodium channel gene (vssc). In this study, the pyrethroid resistance state of the German cockroach in the Republic of Korea (ROK) was assessed by analyzing the frequencies of kdr mutations using one-step PCR with total RNA. The results revealed that among the 25 populations examined, 14 populations exhibited the L993F kdr mutation, while no other mutations were detected. Since other cockroach species are also commonly found in human dwellings in ROK, the vssc genes were cloned from four other species, including Blattella nipponica, Periplaneta americana, Periplaneta japonica, and Periplaneta fuliginosa. Based on the genomic DNA (gDNA) sequences obtained from the vssc cloning, primer sets were designed to amplify the vssc fragment spanning the L993F mutation for each species and used to monitor the development of pyrethroid resistance in cockroach populations in the ROK. The study will facilitate the implementation of a nationwide monitoring program to assess cockroach resistance and select suitable alternatives.

Acetylcholinesterase (AChE) is a key enzyme that terminates impulse transmission by rapidly hydrolyzing the neurotransmitter acetylcholine at cholinergic synapses. Previous studies have discovered a transiently opening channel referred to as the “back door” in Torpedo californica AChE. Previously, we observed that substituting the Tyr391 residue with a Phe residue significantly decreased the catalytic efficiency of recombinant Apis mellifera AChE1 (AmAChE1), while the reverse substitution restored it. Interestingly, substitution of the Tyr391 residue with a Phe residue in AmAChE1 disrupted the formation of the backdoor, while the reverse substitution restored it. This finding suggests that the Tyr-to-Phe substitution impairs backdoor formation, thereby leading to a significant reduction in the catalytic activity of AmAChE1. This serves as one of the driving forces for the functional transition from AmAChE1 to AmAChE2. In this experiment, we also confirmed the gradual restoration and increase in AChE activity by substituting Phe391 in AmAChE1 with Ser, Trp, Thr, Ile, Asn, and Tyr residues through kinetic assay and molecular dynamics simulation.

Medically significant indoor/ectoparasitic insect populations, including bed bugs and head lice, have developed considerable resistance to insecticides due to limited introduction of new genetic traits and the absence of an overwintering barrier. In contrast, outdoor pests like Anopheles and Culex mosquitoes exhibit fluctuating resistance patterns, likely influenced by factors such as overwintering barriers and relatively wider open habitats. Mosquitoes also face selection pressure from diverse sources beyond public health insecticides unlike bed bugs or head lice. Understanding different factors driving resistance among pests is essential for effective resistance management.

전 세계적으로 농업해충의 약제 저항성 발달에 따른 방제 효율 저하는 농약의 과다 사용을 초래하여 농업의 생산성 저하 및 환경 파괴 문제 등을 야기하고 있다. 뿐만 아니라 위생해충의 경우에도 약제 저항성 발달이 심각한 수준으로 나타남에 따라 인류 보건에 큰 위협이 되고 있다. 해충의 약제 저항성은 자연계에 존재하는 극히 낮은 빈도의 저항성 형질이 반복적인 약제 사용에 따라 선발되는 과정을 통해 발달 되는데, 해충 약제 저항성의 효과적 관리를 위해서는 저항성 발달 기작의 규명과 신속·정확한 진단법의 확립이 필수적이다. 현재까지의 저항성 관리 는 저항성 발달 후 대응적(reactive)으로 이루어져 왔으나, 미래에는 보다 다양한 분자 마커를 활용하여 저항성 형질 빈도를 관리 가능한 수준에서 유지하는 선제적(proactive) 저항성 관리도 가능할 것으로 예상하고 있다. 본 발표에서는 해충 약제 저항성 연구의 현재 상황과 미래 전망에 대해 소개하고자 한다.

2022년 국내 노지 마늘, 대파, 양파, 부추 작물재배지에서 채집한 파총채벌레 지역집단들에 대하여 살충제 저항성을 조사하였다. 제조사 추천약량에서의 살충력은 acrinathrin SC를 제외한 6종 약제들이 안성 등 8개 집단 에서 모두 90%이상을 보였으며, Spinetoram SC와 fluxametamide EC는 추천농도의 100배 희석농도에서도 전 지역 집단에 걸쳐 높은 살충력을 보여주었다. 미리 저항성 진단농도로 코팅한 바이알을 이용한 지역집단의 저항성 검정을 실시한 결과, emamectin benzoate의 저항성이 신안 등 9개 지역집단에서 매우 높았으며, chrantraniliprole은 부산 등 4개 , spinetoram은 의성 등 3개, actamiprid와 chlorfenapyr는 각각 1개의 지역집단에서 저항성이 높게 발달 하고 있는 것을 확인할 수 있었으며, 지역별로는 주요 대파 및 양파 재배지인 안성, 서산, 진도, 신안 지역의 저항성 이 모든 약제에 대하여 전반적으로 높게 나타났다.

The onion thrips, Thrips tabaci (Thysanoptera: Thripidae), is a worldwide pest that causes serious damage to Allium crop species and acts as a vector for iris yellow spot virus (IYSV). In a previous study, we established an emamectin benzoate (EB) resistant strain (EB-R) with a 490-fold higher resistance ratio than the susceptible strain (SUS). The EB-R exhibited significantly increased transcript levels of glycine receptor alpha, glutamate-gated chloride channel (GluCl) b, and cytochrome P450 (CYP450) 6EB2 compared to SUS. To identify EB resistance-related genes that are differentially expressed genes between SUS and EB-R, we established an isogenic backcrossing strain and conducted transcriptome analysis after the 4th cycle of isogenic backcrossing. Among the 85 up-regulated genes in the transcriptome data, six cuticular protein genes showed up-regulation. Additionally, CYP450 4g15, which catalyzes the synthesis of cuticular hydrocarbons, exhibited a 6 log2-fold higher expression level in EB-R compared to SUS. Therefore, the elevated expression of genes associated with cuticle protein modification may be significantly is involved in the development of EB resistance.

In Korea, the Asian honey bee (Apis cerana) and the European honey bee (Apis mellifera) (Hymenoptera: Apidae) are the two most common honey bee species. These two closely related species are known to have different sensitivity levels to various insecticides due to millennia of exposure to different pests and pesticides. It is reported that A. cerana is known to be more sensitive to several insecticides, such as amitraz, fenitrothion, and fipronil, than A. melllifera. Multiple studies investigated toxicological responses and related CYPome in A. mellifera, but little is known in A. cerana. The goal of this study is to elucidate the underlying mechanism of different toxicological responses between two bee species, with an emphasis on cytochrome P450 (P450), a significant enzyme involved in metabolic activities. The differences in basal P450 expression patterns were investigated by comparing the relative expression levels of P450 orthologs in several dissected organisms of each species. To compare the sensitivity against major insecticides, lethal doses of major insecticides relevant to both honey bee species were assessed by topical and oral ingestion bioassays. The determined sublethal doses of insecticides were applied to honey bees, and the inducibility of P450s was investigated by comparing the expression patterns of multiple P450s. From these results, this study eventually attempts to compare the toxicological differences between two Apis species with differences in induced cytochrome P450 expression levels.

The Varroa mite, Varroa destructor, a parasitic mite that afflicts honey bees, has become increasingly resistant to acaricides like fluvalinate due to its widespread use. The target site insensitivity mechanism, mediated by the L925V/M/I mutations in the voltage-gated sodium channel, plays a major role in resistance. Additionally, cytochrome P450 monooxygenases (Cyp450s) appear to function as a metabolic resistance factor; however, no Cyp450-mediated resistance mechanism has been reported to date. The aim of this study was to identify and characterize Cyp450s associated with fluvalinate resistance. A synergistic bioassay confirmed the involvement of Cyp450s in conferring tolerance or resistance to fluvalinate. Correlation analysis between mortality data and the expression levels of Cyp450 genes led to the identification of several candidates that may play a crucial role in fluvalinate resistance. Analysis of tissue distribution patterns revealed that these genes were most abundantly expressed in the cuticle and synganglion. This suggests that, despite their relatively low expression level, they may play a critical role in protecting the target site from fluvalinate due to its predominant expression in neuronal tissues. Functional analysis, in conjunction with baculovirus expression, demonstrated that fluvalinate has high inhibition rates against the recombinant candidate Cyp450s, suggestive of their strong interaction with fluvalinate. We discussed the potential utilization of their expression levels as a molecular marker for diagnosing metabolic resistance in field-collected Varroa mites.

The Varroa mite, Varroa destructor is an ectoparasite that parasitizes honey bees. The widespread usage of acaricides, particularly fluvalinate, has resulted in the emergence of resistance in Varroa mite populations all over the world. The goal of this study is to track fluvalinate resistance in Varroa mite field populations in Korea using both bioassay and molecular markers. To accomplish this, a residual contact vial (RCV) bioassay for on-site resistance monitoring was developed. Early mortality evaluation in the RCV bioassay was effective for reliably separating mites with the knockdown resistance (kdr) genotype, but late mortality evaluation was useful for distinguishing mites with additional resistance factors. The RCV bioassay of 14 field mite populations collected in 2021 revealed potential resistance development in four populations. Quantitative sequencing was used as an alternate method to examine the frequency of the L925I/M mutation in the voltage-gated sodium channel (vgsc), which is related with the fluvalinate kdr phenotype. While the mutation was not present in Varroa mite populations in 2020, it appeared in 2021, rose in frequency in 2022, and was practically ubiquitous across the country by 2023. This recent emergence and rapid spread of fluvalinate resistance within a span of three years demonstrate the Varroa mite's significant potential for developing resistance. This situation emphasizes the critical necessity to replace fluvalinate with alternate acaricides, such as fenpyroximate, coumaphos, and amitraz. A few novel vgsc mutations potentially involved in resistance were identified. Potential factors driving the rapid expansion of resistance were further discussed.